1. Field of the Invention
The present invention relates to a vehicle brake device for controlling braking force applied to a vehicle in response to an amount of a brake depression operated by an operator of the vehicle.
2. Discussion of the Related Art
It has been known that a vehicle brake device that is provided with a master cylinder which supplies wheel brake cylinders with brake fluid, a conduit hydraulically connecting the wheel brake cylinders and the master cylinder and an electromagnetic valve disposed in the conduit for generating a predetermined hydraulic pressure differential between the wheel brake cylinders and the master cylinder. In such conventional vehicle brake device, the electromagnetic valve controls the flow of the brake fluid in response to an electric power supplied thereto. Further, a method for obtaining an operating characteristic (such as, for example, a relationship between the minimum valve opening electric current and the hydraulic pressure differential) of an electromagnetic valve constituting a vehicle brake device is disclosed in, for example, JP2004-237982 A (Patent Document 1). According to this disclosed method, the pressure in the conduit in which an electromagnetic valve is disposed, is detected and measured and the operating characteristics are determined based on the measured value of the pressure.
However, according to the structure of the conventional vehicle brake device, the pressure change in the conduit, in which the electromagnetic valve is disposed, tends to be fluctuated or deviated among the individual valves, at the time the electromagnetic valve is opened. Particularly, the pressure in the conduit at wheel brake cylinder side, relative to the electromagnetic valve, tends to be more deviated than the deviation occurred at the other side, the master cylinder side, due to some wheel cylinder structural reasons. Accordingly, when the operating characteristics of the electromagnetic valve disposed in the conduit between the master cylinder and the wheel cylinders are obtained according to a method disclosed in the above Patent Document 1, the setting of the operating characteristics may be affected by such pressure deviation or deviation and it is not easy to accurately determine the operating characteristics.